The invention relates to the dialkoxybenzylidenecamphor derivatives of the formula I ##STR2## in which R.sup.1 and R.sup.2, in each case independently of one another, are a straight-chain or branched alkyl radical having 1 to 10 C atoms, and
X is H or SO.sub.3 H PA0 3-(2',5'-dimethoxybenzylidene)camphor PA0 3-(2',5'-diethoxybenzylidene)camphor PA0 3-(2',5'-dipropoxybenzylidene)camphor PA0 3-(2',5'-dimethoxybenzylidene)camphor-10-sulfonic acid PA0 3-(2',5'-diethoxybenzylidene)camphor-10-sulfonic acid PA0 3-(2',5'-dipropoxybenzylidene)camphor-10-sulfonic acid. PA0 R.sup.4 is an alkyl radical having 1 to 4 carbon atoms.
and to a process for their preparation and their use in cosmetic preparations, in particular for protection from solar radiation, and in pharmaceutical preparations for the prophylactic treatment of inflammations and allergies of the skin or certain types of cancer.
As is known, the skin has a sensitive reaction to solar rays, which can cause ordinary sunburn or erythema, but also more or less pronounced burning.
Solar rays, however, have other negative effects: they cause the skin to lose its elasticity and to form wrinkles and thus lead to premature aging. In some cases, dermatoses can also be observed. In the extreme case, certain types of skin cancer, such as melanoma, occur in some people.
It is also desirable to protect hair against photochemical damage in order to prevent changes in color shades, bleaching or damage of a mechanical type.
It is known that components contained in cosmetic preparations are not always sufficiently stable to light and decompose under the action of light rays.
As is known, the most hazardous part of the solar rays is formed of the ultraviolet rays having a wavelength of less than 400 nm. It is also known that owing to the presence of the ozone layer of the earth's atmosphere, which absorbs a part of the solar radiation, the lower limit of the ultraviolet rays which reach the earth's surface is at about 280 nm.
It thus appears desirable to make available compounds which can absorb UV rays in a wavelength range from 280 to 400 nm, i.e., also UV-B rays having a wavelength between 280 and 320 nm, which play a decisive role in the formation of sun erythema, and also UV-A rays having a wavelength between 320 and 400 nm, which can tan and also age the skin, promote the induction of an erythematous reaction or increase this reaction in certain people or can even induce phototoxic or photoallergic reactions.
The sunscreen filters customary nowadays in cosmetics are divided into UVA and UVB filters. While in the UVB range (280-320 nm), substances such as Eusolex.RTM. 6300 (3-(4-methylbenzylidin)-camphor) or Eusolex.RTM. 232 (4-phenyl-benzimidazole-5-sulfonic acid) make good filters, those used in the UVA range (320-400 nm) are affected by problems: Dibenzoylmethanes such as Parsol.RTM. 1789 (butylmethoxydibenzoylmethane) or Eusolex.RTM. 8020 (isopropyldibenzylmethane) are not indefinitely stable under UV irradiation, which on the one hand reduces the filter effectiveness with time and on the other hand can promote photosensitization of the skin in isolated cases. The benzophenones also used as UVA filters are only soluble to a limited extent in the oils used in cosmetics, and they have a relatively low absorption. On the other hand, only a few water-soluble UVA filters are known at present whose UV absorption, however, is low.
Similar benzylidenecamphor derivatives are disclosed in DE-OS 3,833,706. However, these have at least one tertiary alkyl group. These compounds can also be used as UV filters in sunscreen compositions, but, because of the phenolic hydroxyl group, are rather more suitable as antioxidants. Because of their tertiary alkyl group, these compounds are only soluble to a limited extent in conventional cosmetic vehicles, in particular in aqueous suspensions, so that in sunscreen compositions they always have to be employed together with other UV filters.